1. Field of the Invention
This invention relates to switching techniques in the field of wireless communication, and more particularly, to a femtocell base station and a method of switching communication services automatically switch between femtocell base stations when a mobile communication apparatus enters a communication coverage supplied by plural femtocell base stations.
2. Description of Related Art
In the course of development of communication network, network coverage is always an issue of network construction to operators and is also one of the considered elements for customers to choose an operator. Currently, wide area network coverage is quite stable. For example, a macro cell base having large coverage may be applicable to a user flow which has sparse population and fast mobile rate. Even in a remote country, it also achieves wide area network coverage.
However, in terms of a densely populated city, followed by the condition of increased high building density and mobile users in buildings, the indoor area is always a area of weak macro cell system network coverage. Therefor; a micro cellular base station (also referred to femtocell base station) is generated. The described femtocell (Femtocell) base station extends the coverage of mobile communication and solves the problems of weak network coverage of indoor area.
As is well known, switching of a mobile communication terminal (such as a cellular phone) between macro cellular base stations is actually a process of signal comparison, that is, when the mobile communication terminal detects plural surrounding macro cellular base stations simultaneously, it will tend to select a macro cellular base station having larger signal intensity as a connection object. Since the connection of the macro cellular base stations is accomplished by optical fibers, information exchange rate between the macro cell bases is very quick. In other words, signal comparison between macro cellular base stations is synchronous comparison and thus it does not exist a time delay phenomenon. Therefore, there is no comparison distortion between the macro cellular base stations which results in condition of that the mobile communication terminal is switched to a macro cellular base station which does not have the best communication quality.
However, in an architecture of a femtocell base station, the connection between the femtocell base stations is accomplished by network cables. Since transmission rate of a network cable is far less than transmission rate of an optical fiber, it can not perform synchronous comparison of signals between the femtocell base stations as being between the macro cellular base stations. Thus, when the femtocell base station performs comparison of signal intensity, the femtocell base station performing comparison judgment can not immediately capture immediate signal parameters (i.e., signal intensity) of another femtocell base station. Hence, it will generate comparison distortion due to poor reliability of captured signal parameter such that the signal weakens after being switched to another femtocell base station, thereby not accurately and successfully accomplishing system switching.
Therefore, it is imperative for people in related field to how to design a femtocell base station and its switching technique which may improve shortcomings of prior arts.